The oldest DNA reveals life in Greenland 2 million years ago

NEW YORK — Scientists have found the oldest known DNA and used it to reveal what life was like 2 million years ago on the northern tip of Greenland. Today it is a barren arctic desert, but back then it was a lush landscape of trees and vegetation with numerous animals, even the now-extinct mastodon.

“The research opens the door to a past that was actually lost,” said lead author Kurt Kjær, a geologist and glacier expert at the University of Copenhagen.

Because animal fossils are hard to find, researchers extract environmental DNA, also known as eDNA, from soil samples. This is the genetic material that organisms shed into their environment – for example through hair, waste, spit or decomposing carcasses.

Studying really old DNA can be challenging because genetic material breaks down over time, leaving scientists with only small fragments.

But with the latest technology, researchers have been able to extract genetic information from the small, damaged pieces of DNA, explained senior author Eske Willerslev, a geneticist at the University of Cambridge. In their study, published Wednesday in the journal Nature, they compared DNA with that of different species, looking for matches.

The samples come from a sedimentary deposit called the Kap København Formation in Peary Land. Today, the area is a polar desert, Kjær said.

But millions of years ago, this region underwent a period of intense climate change that caused temperatures to rise, Villerslev said. The sediment probably accumulated over tens of thousands of years at the site before the climate cooled and cemented the finds into the permafrost.

The cold environment would have helped preserve the delicate bits of DNA — until scientists came along and broke through the samples, starting in 2006.

During the region’s warm period, when average temperatures were 20 to 34 degrees Fahrenheit (11 to 19 degrees Celsius) warmer than today, the area teemed with an unusual array of plant and animal life, the researchers report. The DNA fragments suggest a mixture of arctic plants, such as birch trees and willow bushes, with those that normally prefer warmer climates, such as firs and cedars.

DNA also shows traces of animals, including geese, rabbits, reindeer and lemmings. Previously, a dung beetle and the remains of a rabbit were the only signs of animal life at the site, Villerslev said.

One big surprise was the discovery of DNA from the mastodon, an extinct species that looks like a cross between an elephant and a mammoth, Kjær said.

Many mastodon fossils have previously been found in the temperate forests of North America. It’s an ocean away from Greenland and much further south, Villerslev said.

“In a million years, I wouldn’t expect to find mastodons in northern Greenland,” said Lav Dahlen, an evolutionary genomics researcher at Stockholm University who was not involved in the study.

As the sediment accumulated at the mouth of the fjord, the researchers were also able to obtain clues about marine life from this period. The DNA suggests that horseshoe crabs and green algae lived in the area — meaning the nearby waters were likely much warmer then, Kjær said.

By extracting dozens of species from just a few sediment samples, the study highlights some of the advantages of eDNA, said Benjamin Verneau, an ancient DNA researcher at Germany’s Max Planck Institute for Evolutionary Anthropology, who was not involved in the research.

“You really get a bigger picture of the ecosystem at a certain point,” Verneau said. “You don’t have to go and find that piece of wood to study that plant and that bone to study that mammoth.”

Based on the available data, it’s hard to say for sure whether these species really lived side by side or whether the DNA was mixed from different parts of the landscape, said Laura Epp, an eDNA expert at Germany’s University of Konstanz, who was not involved in the study. .

But Epp said this kind of DNA research is valuable for showing “hidden diversity” in ancient landscapes.

Willerslev believes that because these plants and animals survived a time of dramatic climate change, their DNA may offer a “genetic road map” to help us adapt to the current warming.

Stockholm University’s Dahlen expects ancient DNA research to continue delving deeper into the past. He worked on the study, which previously held the record for the “oldest DNA” from a mammoth tooth about a million years old.

“I wouldn’t be surprised if you can go back at least one or maybe a few million years, assuming you can find the right samples,” Dahlen said.

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